Cell lines are powerful tools for research into liver function at the molecular level. However, they are generally unsuitable for rigorously assessing the effects of amino acid composition, because many lines require serum-containing medium for their maintenance. Here, we aimed to investigate the effects of ornithine and arginine, which are included in the characteristic metabolic process in hepatocyte, on a human hepatoma-derived cell line (FLC-4) that can be cultured in serum-free medium. FLC-4 cells were cultured under the following three conditions: + ornithine/ – arginine, – ornithine/ – arginine, and –ornithine/ + arginine. Albumin expression evaluated by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay and showed no obvious differences based on the presence of ornithine or arginine. However, the mRNA levels of two liver-enriched transcription factors (CEBPB and HNF1A), which are involved in regulating albumin expression, were significantly higher in cells grown in medium-containing arginine than that in cells grown in ornithine-containing medium. Western blotting showed that the levels both activating and inhibitory C/EBPβ isoforms were significantly increased in cells grown in arginine medium. Furthermore, we have found that depletion of both ornithine and arginine, the polyamine sources, in the medium did not cause polyamine deficiency. When ornithine and arginine were depleted, albumin production was significantly reduced at the mRNA level, CEBPB mRNA levels were increased, and the level of activating form of C/EBPβ was increased. The results of this study suggest that in hepatocyte, these two amino acids might have different functions, and because of which they elicit disparate cellular responses.

中文翻译：

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研究尿素循环氨基酸对人肝癌细胞系FLC-4中ALB和CEBPB表达的影响。

细胞系是在分子水平上研究肝功能的强大工具。但是，它们通常不适合严格评估氨基酸组成的作用，因为许多品系需要使用含血清的培养基进行维护。在这里，我们旨在研究鸟肝素和精氨酸对人肝癌衍生细胞系（FLC-4）的影响，其中鸟氨酸和精氨酸包括在肝细胞的特征性代谢过程中，该细胞系可在无血清培养基中培养。FLC-4细胞在以下三个条件下培养：+鸟氨酸/ –精氨酸，–鸟氨酸/ –精氨酸，和–鸟氨酸/ +精氨酸。通过定量聚合酶链反应和酶联免疫吸附试验评估白蛋白表达，基于鸟氨酸或精氨酸的存在，无明显差异。然而，参与调节白蛋白表达的CEBPB和HNF1A）在含精氨酸培养基中生长的细胞中显着高于在含鸟氨酸培养基中生长的细胞中。Western印迹显示，在精氨酸培养基中生长的细胞中，活化和抑制性C /EBPβ同工型的水平均显着增加。此外，我们发现在培养基中耗尽鸟氨酸和精氨酸（多胺源）都不会引起多胺缺乏。当鸟氨酸和精氨酸被耗尽时，在mRNA水平，白蛋白的产生显着减少，CEBPBmRNA水平增加，并且激活形式的C /EBPβ水平增加。这项研究的结果表明，在肝细胞中，这两个氨基酸可能具有不同的功能，因此它们引起不同的细胞反应。